The metabolism of the nitrogenous bases, choline and ethanolamine in isotopic form, will be investigated in various regions of the monkey brain in the non-tolerant and tolerant state with respect to morphine and other narcotics. Special emphasis will be placed on the biosynthesis of phosphatidylcholine and phosphatidylethanolamine and ancillary reactions in their metabolism. Isotopic bases will be injected intravenously as well as into specific intracerebral sites by means of stereotaxic instruments. The labeling of phosphatides in subcellular fractions of brain tissue after choline and ethanolamine administration also will be investigated. Attempts also will be made to determine whether the intravenous injection of narcotics elicit detectable cytological alterations in quantities of DNA and RNA, and the dendritic structure of individual neurons. These aims will be accomplished by employing the Golgi method, Feulgen reaction, and azure-B stain after pretreatment with DNase.